The customary embodiments of running gear are of two types as far as the wheel rims are concerned. They are produced either with what are known as drop-center rims, which have tapered bead seats inclined by an angle of 5° or 15° with respect to the axis of rotation of the assembly, or with flat or practically flat base rims which have bead seats inclined either by 0° or by 5° with respect to the axis of rotation.
Drop-center rims have a mounting groove the diameter of which is markedly smaller than the nominal diameter of the rim. This internal diameter of the rim is considered by users to be too small because it does not, for example, allow brake drums to be selected that are of a size suited to effective braking of vehicles which are becoming increasingly powerful with respect to their weight.
As a result, the rims are commonly used for mounting and running, for example, tires of passenger vehicles and/or heavy goods vehicles, but are used far less, if at all, for other types of vehicles such as, for example, earth-moving and construction equipment.
In order to fit tires, particularly tires of the tubeless type, a flat base rim requires there to be at least one removable lateral ring, a locking ring and a seal, and obviously the base of the rim to have a fixed flange on the opposite side to the side on which the parts are removable. This is because the dimensions of the wheels of the vehicles and the dimensions of the tires, particularly the stiffness of the lower regions, entail producing the wheels in multiple parts so as to allow the tire to be mounted on a rim. It is therefore necessary to have at least three parts. In most cases, the number of parts needed is greater than three and may sometimes be as many as six parts for large-sized tires, not including the parts needed to fix the wheels to the vehicle. With the exception of the seals which are made of rubber, the parts of a wheel rim are made of metal and are therefore heavy, bulky and difficult to handle. It therefore follows that mounting and removing large and very large tires are difficult and lengthy operations. Fitting and/or removing a wheel equipped with such a tire involves laying up the vehicle or the equipment for a length of time that is rather considerable and therefore prejudicial to the desired productivity in the use of these vehicles.
Patent Application WO 00/71365 describes a technique that allows the mounting of tires to be simplified, these tires being mounted directly on the hub which then acts as a rim. Independent mounting rings act as the bead seats and are held in place by lock rings which can be secured to the hub using, in particular, complementary profiles. With this technique, the locking ring is made up of a vulcanized rubber compound reinforced by and coated onto a reinforcing ring that is circumferentially elastic and radially resistant to compression.
A technique such as this is very advantageous because it makes it possible to eliminate the phases of mounting onto a rim and of fixing a wheel to the vehicle, the tires being mounted directly onto the hub via the mounting rings and locking rings. Furthermore, since the number of elements is greatly reduced, the phases involved in handling these elements become simpler.
Tests conducted on this type of technique have revealed the fact that the locking ring, which, aside from its function of locking the system, is an element involved in the transmission of braking or driving torque, undergoes loading which causes it to wear. The locking ring which, at its surface, exhibits a rubber compound in order to give it elasticity and provide control over the coefficients of friction, particularly between the hub of the vehicle and the locking ring, therefore in use is subjected to wearing of its outer part which comes into contact with the hub on the one hand, and a mounting ring on the other hand, both of these being made of metal. This wear results in the need to change the locking ring each time the tire is changed. The complex nature of this element which is made up of a rubber compound coating an annular reinforcing element that is resistant to compression and the need to change it periodically leads to additional costs that must be borne by the user.